This invention relates to a cartridge based data storage system in which a flexible magnetic disk is disposed within a cartridge shell. More particularly, the invention relates to a double shelled cartridge for controlling access to the disk media.
Microprocessors and supporting computer technologies are rapidly increasing in speed and computing power while decreasing in cost and size. These factors have led to the broad application of microprocessors to an array of electronic products, such as hand-held computers, digital cameras, cellular phones and the like. All of these devices have, in effect, become computers with particular application-specific attributes. For this new breed of computer products, enormous flexibility is gained by the ability to exchange data files and store computer software.
A variety of proprietary storage devices have been used in computer products. For example, hand-held computers have used integrated circuit memory cards ("memory cards") as the primary information storage media. Memory cards include memory storage elements, such as static random access memory (SRAM), or programmable and erasable non-volatile memory, such as "flash" memory. Memory cards each are typically the size of a conventional credit card and are used in portable computers in place of hard disk drives and floppy disk drives. Furthermore, memory cards enhance the significant advantages of the size, weight, and battery lifetime attributes of the portable computer and increase portability of the storage media. However, because of the limited memory density attainable in each memory card and the high cost of the specialized memory chips, using memory cards in hand-held computers imposes limitations not encountered in less portable computers, which typically use more power-consuming and heavier hard and floppy disk drives as their primary storage media.
Other of these computer products, such as the digital camera, have employed miniature video disks as the storage media. For example, U.S. Pat. No. 4,553,175 issued Nov. 12, 1985 to Baumeister discloses a digital camera configured to store information on a magnetic disk. In Baumeister, a signal processor receives signals representative of a picture from a photo sensor. Those signals are recorded on a magnetic disk for later processing. Unfortunately, the video disk storage product provides limited storage capacity. For that and other reasons (e.g., power consumption and cost), the video disk has not been used in other computer products. As a result, interchanging data from one of these digital cameras with other computer products, such as a hand-held computer, is not readily achieved.
Miniature hard disk drives have also been suggested for use in portable computer products. For example, U.S. Pat. No. 5,469,314 issued Nov. 21, 1995 to Morehouse et al. discloses a miniature hard drive for use in portable computer applications. In Morehouse, a hard disk drive is described that is approximately 50 mm in diameter. While addressing many of the problems presented by storage requirements in portable computers, the obvious problem of removability of the storage media is still present.
Similar to a standard size cartridge, the miniature cartridge contains a flexible magnetic disk disposed within a hard outer shell. Such a standard size cartridge is disclosed in U.S. Pat. No. 4,445,157 (Takahashi). The Takahashi patent is generally directed to a disk cassette that contains a flexible magnetic disk having a center core (i.e., a hub) and an apparatus for reading and recording information on the flexible magnetic disk. The disk cassette comprises a flexible disk attached to a hub. The disk and hub assembly are sandwiched between an upper cover and a lower cover. The shutter slides over the outside of the cartridge to cover a head access opening.
A similar standard size cartridge is disclosed in U.S. Pat. No. Re, 32,876 (Wakabayashi et al.). The Wakabayashi patent is also generally directed to a disk cassette that contains a flexible magnetic disk having a center core (i.e., a hub) and for storing information. The disk cassette comprises a flexible disk attached to a hub. The disk and hub assembly are sandwiched between an upper cover and a lower cover. The Wakabayashi shutter rotates on the interior of the cartridge and comprises a metal sheet that slides over a disk access opening to cover a head access opening. This interior shutter works okay for disk that have low revolution speed in which aero dynamics of the disk are not an issue. However, in a cartridge wherein the disk rotates at relatively high velocities, the shutter could change the aerodynamics of the disk rotation and effect performance.
Thus, there is a need for an improved shutter mechanism.